Lasers have been used in a variety of medical applications, including the treatment of atherosclerotic plaque which builds up on the walls of arteries and can create cardiovascular problems by restricting arterial flow. In order to properly apply the laser energy, it is necessary to obtain an image of the area that is to undergo treatment. For example, U.S. Pat. No. 4,576,177 to Webster discloses a catheter which includes optical fibers for transmitting laser energy and an ultrasonic transducer at the tip end of the catheter for obtaining ultrasonic images. Electrical wires extend through the catheter to provide power for operating the ultrasonic transducer and to transmit image information sensed by the transducer.
Pending application Ser. No. 672,822 filed on Mar. 21, 1991 in the name of Thomas R. Winston for "Catheter for Laser Treatment of Atherosclerotic Plaque and other Abnormalities" discloses a number of different catheter constructions that improve upon the catheter shown in the Webster patent. Pending application Ser. No. 824,023 filed on Jan. 22, 1992 in the names of Thomas R. Winston and John M. Neet for "Medical Catheter Using Ultrasound Mapping With External Transducers" discloses yet another improvement in which the ultrasonic transducer is external to the catheter.
In the arrangement shown in the latter application, separate optical fibers are used to transmit the ultrasonic signals and the laser energy. While this is entirely satisfactory in some applications, there are other applications in which the need to provide separate fibers for the ultrasound and laser energy is a significant disadvantage.